This invention relates to a liquid filled vibration isolating device mainly used for supporting a vibration generating body such as an engine of an automobile.
The liquid filled vibration isolating device supports a vibration generating body such as an engine of an automobile while preventing the transmission of the vibration of the vibration generating body to a vehicle body or the like. It is known a type of liquid filled vibration isolating device which is constructed such that; a partitioner is provided for dividing a liquid chamber in a vibration isolating device body into a main liquid chamber and a sub liquid chamber; and an orifice which communicates the main liquid chamber with the sub liquid chamber is formed in the partitioner; and the vibration attenuating function is achieved by the effect of flowing of liquid in the liquid chambers through the orifice. Furthermore, recently, a double-orifice-type of liquid filled vibration isolating device is. known which has two orifices in the partitioner for attenuating the vibrations of different frequencies has been known.
For example, JP-A-09100866 (Japanese Patent Publication, unexamined, 9-100866(1997)), hereinafter referred to Prior art 1, proposes a vibration isolating device where an upper side of first partition member on a main liquid-chamber-side is covered with second partition member which adheres a sub diaphragm thereto by vulcanization, so as to define a third liquid chamber in an inner portion of the partition members; and a second orifice is formed to communicate with the third liquid chamber; whereby one orifice passage is for preventing low-frequency shake vibrations while another orifice passage in for preventing high-frequency idle vibration.
Furthermore, JP-A-09210117 (Japanese Patent Publication, unexamined, 9-210117(1997)), herein after referred to Prior art 2, proposes a vibration isolating device where a sheet of elastic member which is formed by vulcanization is clamped between a partition member and a restricting member defining a sealed air chamber, thus constituting two diaphragms of different modulus of elasticity from a sheet of elastic member; and between the partition member and these diaphragms, a liquid chamber which is communicated with an orifice formed in an outer peripheral portion of the partition member and a second liquid chamber which is communicated with a second orifice formed in an inner portion of the partition member are defined so that the vibration isolating device can cope with the vibration of wide frequency band such as the shake vibration and the idle vibration.
In such double-orifice liquid filled vibration isolating devices, particularly, the length and the cross sectional area of the orifice formed in the partitioner, and furthermore, the modulus of elasticity of both diaphragms become important parameters for achieving a given vibration attenuating function. The durability and the sealing ability to maintain this vibration attenuating function also become important. Furthermore, the easiness of assembling the partitioner to a vibration isolating device body must be taken into account.
From this viewpoint, the inventors have reviewed the reliability,.the easiness of mounting (shape and size of caulking portions), the functionality, and the easiness of assembling of products of the Prior arts 1 and 2. With respect to the Prior art 1, the vibration isolating device is constructed such that the lower partitioner member is fitted into the bowl-shaped upper partitioner member which opens downwardly; and orifices defined by these upper and lower partitioner members are respectively formed in the outer-peripheral side and the inner side of the lower partitioner member. Accordingly, there arises a problem with respect to the maintenance of the sealing ability of the orifices. Furthermore, the high accuracy of dimension of the upper and lower partitioner members is required.
On the other hand, with respect to the Prior art 2, two diaphragms which differ in the modulus of elasticity are formed of one elastic member so that, at the time of assembling, it is necessary to pay an attention to the shape of the caulking portion so as to prevent the dimensional variation or dimensional tolerance between the elastic member and the partition member from becoming large and hence, the caulking operation becomes difficult. Furthermore, in case the dimensional variation or dimensional tolerance becomes large, it gives an adverse effect to the cross sectional area of the orifices and the modulus of elasticity of the diaphragms thus living rise to problems which affects the functionality of the equipment.